# How to rotate an object along the Y axis to the right, and then to the left?

How to rotate an object along the Y axis to the right, and then to the left by a certain number of degrees. The object moves and rotates randomly, so the starting angle can be any.

Sine wave.

Mathf.Sin(x); outputs a value that will go from zero, up to one, then down to -1 and back to zero at a constant, smooth rate as you increase the value of x. Use that, along with the Quaternion.Euler(); method.

Want more than 1 degrees change? No problem! Multiply the output of Mathf.Sin(x); by the maximum number of degrees you want. At 1, you’ll have all your degrees, at 0, you’ll have none and at -1, you’ll be looking the other direction.

Alternatively, look into Mathf.Pingpong();

void Update
{

``````    float y = 5; //easy variable for y

this.gameObject.transform.localEulerAngles = new Vector3(0, y, 0);

}
``````

This changes the local y angle to 5 degrees, you can also just use EulerAngles for worldspace angles instead of local. As for wanting to change it I assume you want it over time otherwise its gonna twitch out. I recommend using an IEnumerator for that if its always running else Update will work fine, just be sure to set a speed and multiply it by DeltaTime. Deltatime ensures a smooth transition over time, otherwise your code runs once a frame and any transforms will be done way to fast.

``````private float y = 0; //we need to store the variable outside so to not have it reset every time update is called.
public float rotationSpeed = 5; //This is a public variable that we can change for preferred rotation speed.
public float desiredAngle = 30;

void Update
{

//This will increase the angle over time
y += rotationSpeed * Time.deltaTime;
//This changes the local Euler angle(Standard degrees) of y while keeping x and z at 0
this.gameObject.transform.localEulerAngles = new Vector3(0, y, 0);

If (y > desiredAngle || y < 1) //I do this to avoid getting gimble locked
rotationSpeed = -rotationSpeed ; //and with a simple negitave switch we change the direction of the rotation.

}
``````